In a conventional signal transmission device for an elevator, diagnosis signals are transmitted to a plurality of pieces of terminal equipment at a time in a predetermined cycle by diagnosis-signal generation means of an elevator controller. When the diagnosis signals are input to the pieces of terminal equipment, reply signals are output from the pieces of terminal equipment to abnormality detection means. The abnormality detection means checks the replay signal from each piece of the terminal equipment as often as the number of diagnosis signals. Computation means for generating the reply signal in response to the diagnosis signal is provided to each piece of the terminal equipment (for example, see Patent Literature 1).
Moreover, in a conventional abnormality detection device for electric equipment, a pulse which does not interfere with an operation of an electric circuit is superimposed on a normal input signal and is input to the electric circuit. Only when the pulse is output from an output side of the electric circuit, control in a next stage is executed (for example, see Patent Literature 2).